This invention relates to an apparatus for feeding individual rigid plates sequentially out of a stack of plates for separate processing.
In many industrial operations it is necessary to remove rigid plates from a stack and deliver them serially to another location. One method for accomplishing this is to use a vacuum source to adhere the first plate in the stack to a cylindrical carrier which pulls the first plate away from the stack as the carrier rotates. Then when the plate is at the desired location it is deposited by discontinuing the vacuum. The primary problem with using cylindrical carriers for this purpose is that when a rigid plate is removed from a stack the trailing edge of the plate being removed strikes the remaining plates in the stack which disorients the stack and can dislodge the plate being removed. Thus, the plate being carried must be displaced away from the remaining plates in the stack before the carrier is rotated.
This is accomplished by the plate feed apparatus disclosed in U.S. Pat. No. 4,462,745 by creating a cordal segment in the carrier at the location of the air inlet through which the vacuum is drawn. The remainder of the periphery of the carrier then acts as a stop to keep the stack of plates separated from the cordal segment until it becomes aligned with the plates. When the cordal segment does become aligned with the stack the vacuum pulls the front plate in the stack away from the remaining plates up to the cordal segment thereby providing the gap which is necessary to enable the plate to be rotated without striking the remaining plates in the stack. While this apparatus works well to separate plates, as the carrier rotates it rubs on the forwardmost plate in the stack which can cause the plate to become scarred.
What is needed, therefore, is to create the necessary gap between the plate being removed and the rest of the stack while still providing a constant supply of plates in the proper position for removal, without having the rotating carrier rub on the forwardmost plate.
This is accomplished in the present invention by providing a mechanism which is separate from the carrier but which is operably timed by the rotation of the carrier to push the front portion of the stack away from the periphery of the carrier before the vacuum source air inlet opening becomes aligned with the plates. Since the periphery of the carrier is not being utilized to create the gap between the plates and the air inlet opening, the feed mechanism does not need to push the plates up against the carrier and thus they do not rub on the carrier as it rotates.
In a first embodiment of the invention the plates are separated from the carrier by the proper distance by means of rollers which protrude from the periphery of the carrier. One roller is provided for each vacuum inlet opening and it is angularly offset from its associated opening by a 60 degree angle in order that it will be clear of the plate when the plate is in a position to be pulled toward the carrier by the vacuum.
In a second embodiment of the invention a pair of levers are mounted rotatably on the frame of the apparatus outwardly of the sides of the carrier. The levers are arranged to contact the edges of the plate when they are rotated away from the carrier and fit behind the carrier free from the plates when they are rotated toward the carrier. A pair of rollers, one located on each side of the carrier, controls the levers and rotates them forwardly to a first position where the forwardmost plate is separated from the periphery of the carrier by the proper gap before the inlet opening comes into alignment with the plates. Return springs rotate the levers rearwardly to a second position behind the periphery of the carrier when the rollers are not pushing them forward.
In both embodiments a first idler roller is located on the side of the carrier opposite the feed mechanism, with the top of the first idler roller being generally horizontally aligned with the top of the carrier. A belt is wrapped around the first idler roller and the carrier and thus rotates with the carrier to lift the plates being carried by the carrier off of it as they reach its top and transport them to the end of the conveyor belt where they are deposited for further processing. Mounted above the first idler roller is a second idler roller. The idler rollers are separated from one another by a distance that causes the plates to be squeezed between them. As a result the plates remain horizontal until they drop from the rollers.
Accordingly, it is a principal object of the present invention to provide a plate feed apparatus having a rotary carrier in which a uniform gap is created between the plate which is being carried by it and the stack of plates from which it was extracted.
It is a further object of the present invention to provide such a plate feed apparatus in which the gap is not created by the periphery of the carrier itself.
It is a yet further object of the present invention to provide a plate feed apparatus in which the plates are lifted off of the carrier automatically and uniformly at a certain point in its rotation.
It is a still further object of the present invention to provide such a plate feed apparatus where the plates are transported and discharged from the apparatus horizontally after they have been removed from the carrier.
The foregoing and other objectives, features and advantages of the present invention will be more readily understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings.